A stator for an electric machine having stator slots for stator windings, at least one of which can have a cooling fluid flow through it.

Abstract

The present invention relates to a stator (1) comprising a stator body (3) having a plurality of stator teeth (4) distributed around the circumference and a stator slot (5) formed between the stator teeth (4) and extending axially through the stator body (3), in which a stator winding (6) having a plurality of electrical conductors (7) is arranged, the stator slot (5) having a slot base (8) along its radial extension at its radially outer end and a slot opening (9) at its radially inner end, the electrical conductors (7) of the stator winding (6) having a width (19) and a width (20) of the stator body (3) extending axially through the stator body (3). and a height (10), the width (19) being greater than the height (10), the electrical conductors (7) being arranged in the stator slots (5) such that the width (19) extends circumferentially and the height (10) extends radially, a cooling fluid (12) can flow through at least one, and preferably all, of the stator slots (5), and at least one of the electrical conductors (7) is arranged in at least one of the stator slots (5) through which the cooling fluid (12) can flow, such that the width (19) of the electrical conductor extends radially and the height (10) of the electrical conductor extends circumferentially, at least partially, in the corresponding stator slot (5).

Description

[Technical Field]

[0001] The present invention relates to a stator for an electric machine having a stator body having a plurality of stator teeth distributed around the periphery and stator slots formed between the stator teeth and extending axially through the stator body, wherein a stator winding having a plurality of electrical conductors is arranged in the stator slots, the stator slots along their radial extension having a slot base at their radially outer end and a slot opening at their radially inner end, or the stator slots along their radial extension having a slot base at their radially inner end and a slot opening at their radially outer end, the electrical conductors of the stator winding have a width and a height in cross section, the width being greater than the height, the electrical conductors are arranged in the stator slots such that the width extends circumferentially in the stator slots and the height extends radially within the stator slots, and a cooling fluid can flow through at least one, and preferably all, of the stator slots. [Background technology]

[0002] Electric motors are increasingly being used to drive automobiles to provide an alternative to fossil fuel-hungry internal combustion engines. Significant efforts are already being made to improve the suitability of electric drives for everyday use and to provide users with a familiar and comfortable driving experience.

[0003] A detailed description of an electric drive unit can be found in an article entitled "Highly Integrative and Flexible Electric Drive Unit for E-Vehicles" by Erik Schneider, Frank Fickle, Bernd Cebulski, and Jens Liebold in the German automobile magazine ATZ, Volume 113, May 2011, pages 360-365. The article describes a drive unit for a vehicle axle that includes an electric motor arranged concentrically with a bevel gear differential and a switchable two-speed planetary gear set located in the drive train between the electric motor and the bevel gear differential, also positioned coaxially with the electric motor and the bevel gear differential or spur gear differential. The drive unit is very compact, and the switchable two-speed planetary gear set allows for a good balance between gradeability, acceleration, and energy consumption. Such drive units are also called e-axles or electric drivetrains.

[0004] In addition to purely electrically operated drivetrains, hybrid drivetrains are also known. Such drivetrains in hybrid vehicles typically include a combination of an internal combustion engine and an electric motor, allowing operation in purely electric mode, for example, in urban areas, while simultaneously providing sufficient range and availability, especially on long journeys. Furthermore, in certain driving situations, the internal combustion engine and the electric motor can also be used for drive simultaneously.

[0005] With the development of electric machines for e-axle or hybrid module applications, there is a continuous need to increase their power density, which increases the importance of the cooling of the electric machine. Due to the required cooling capacity, hydraulic fluids such as cooling oils are established in most concepts to remove heat from the thermally loaded areas of the electric machine.

[0006] For example, jacket cooling and winding head cooling are known from the prior art for cooling electric machines with hydraulic fluids: jacket cooling transfers heat generated at the outer surface of the stator lamination core to a cooling circuit, while in the case of winding head cooling, heat transfer takes place directly at the outer conductors of the stator lamination core in the winding head region to the fluid.

[0007] Further improvements are provided by separate cooling channels that are introduced into both the stator lamination core (see, for example, EP 3157138 A1) and the slots in addition to the conductors (see, for example, Markus Schiefer: Indirect Winding Cooling of Highly Utilized Permanently Excited Synchronous Machines with Toothed Coil Winding [Indirect Winding Cooling of Highly Utilized Permanently Excited Synchronous Machines with Toothed Coil Winding], dissertation, Karlsruhe Institute of Technology (KIT), 2017).

[0008] The concept of direct hydraulic fluid flow around the windings to increase power density is also known. Direct contact of the hydraulic fluid with the conductors in the slots improves cooling, and is already known from the prior art. For example, DE 10 2015 013 018 A1 describes a solution for an electric machine with a single-tooth winding, in which the fluid flows directly around the winding wound around the tooth. Summary of the Invention [Problem to be solved by the invention]

[0009] It is therefore an object of the present invention to provide a stator with improved slot cooling that can be manufactured in a particularly cost-effective manner. [Means for solving the problem]

[0010] The object is achieved by a stator for an electric machine, comprising a stator body having a plurality of stator teeth distributed around the periphery and stator slots formed between the stator teeth and extending axially through the stator body, in which a stator winding having a plurality of electrical conductors is arranged, the stator slots along their radial extension having a slot base at their radially outer end and a slot opening at their radially inner end, or the stator slots along their radial extension having a slot base at their radially inner end and a slot opening at their radially outer end, the electrical conductors of the stator winding have a width and a height in cross section, the width being greater than the height, the electrical conductors are arranged in the stator slots such that the width extends circumferentially and the height extends radially in the stator slots, a cooling fluid can flow through at least one, and preferably all, of the stator slots, and at least one of the electrical conductors is at least partially arranged in at least one of the stator slots through which the cooling fluid can flow, in a corresponding stator slot, such that the width extends radially and the height extends circumferentially.

[0011] This has the advantage that flow paths are created within the stator slot in the immediate vicinity of the copper wire without the need for any additional components or features: the electrical conductor itself is used to form the flow paths positioned in alternating cross-sectional directions within the stator slot.

[0012] According to a first preferred embodiment of the present invention, at least two electrical conductors are arranged in a stator slot at a 90° rotation relative to each other, and the basic electrical conductors preferably have a rectangular cross section. Therefore, the 90° rotation of the electrical conductors does not completely fill the stator slot in the circumferential direction, and the remaining gap forms a flow path for the cooling fluid in the stator slot. Most preferably, in a laminated core, a circumferentially protruding protrusion can be formed in the stator slot, which prevents the electrical conductors from displacing in the circumferential direction and therefore ensures a defined flow path shape during stator operation.

[0013] The stator according to the present invention is preferably configured for use in a radial flux machine. Stators for radial flux machines typically have a cylindrical structure and consist essentially of electrical steel sheets that are electrically insulated from one another, structured in layers, and compressed to form a laminated core. Stator slots are distributed around the circumference, embedded in the electrical steel sheets, and arranged substantially parallel to the rotor shaft, and receive the stator winding or portions of the stator winding. The stator slots preferably have a substantially U-shaped cross-sectional profile. Most preferably, the stator slots have linear slot walls extending radially.

[0014] The stator slots of the stator according to the present invention contain embedded stator windings. The stator windings are electrically conductive conductors with a longitudinal extension much greater than their diameter. The stator windings can have virtually any cross-sectional shape. A rectangular cross-sectional shape is preferred because it allows for a high compression density and, therefore, a high power density. The stator windings are particularly preferably made of copper. Preferably, the stator windings have an insulator. To insulate the stator windings, for example, mica paper, which may be reinforced with a glass fiber lining for mechanical reasons, can be wrapped in tape form around one or more stator windings impregnated with a curable resin. In principle, it is also possible to insulate the stator windings without using mica paper and instead use a curable lacquer layer.

[0015] The stator according to the present invention also has a stator body. The stator body can be manufactured in one piece or in multiple pieces, particularly in a segmented form. A one-piece stator body is characterized in that the entire stator body is formed in one piece when viewed from the entire periphery. The stator body is usually formed from a plurality of stacked laminated electrical steel sheets, each of which is closed to form a circular ring. A segmented stator body is characterized in that it is composed of individual stator segments. The stator body can be composed of individual stator teeth or groups of stator teeth, and each individual stator tooth or each individual stator tooth group can be formed from a plurality of stacked laminated electrical steel sheets, each of which is configured as a segmented stator segment.

[0016] The stator body is preferably formed from one or more stator lamination cores, which is understood to mean a plurality of stacked individual sheets or stator laminations, generally made from electrical steel sheets, stacked in layers to form a stack, or what is called a stator lamination core. The individual sheets may then be held within the lamination core by adhesive bonding, welding, or screwing.

[0017] The stator teeth of the stator are preferably formed in the stator body. The stator teeth are components of the stator body configured as circumferentially spaced, radially inwardly facing tooth-like parts of the stator, and an air gap for the magnetic field is formed between the free ends of the stator teeth and the rotor body. The gap between the rotor and the stator is called the air gap. In radial flux machines, this is a substantially annular gap with a radial width corresponding to the distance between the rotor body and the stator body.

[0018] In particular, the stator may be provided for use in an electric machine in a drivetrain of a motor vehicle. The electric machine is particularly intended for use in the drivetrain of a hybrid or fully electric motor vehicle. In particular, the electric machine has specifications such that it can achieve vehicle speeds of more than 50 km / h, preferably more than 80 km / h, in particular more than 100 km / h. The electric machine particularly preferably has a power output of more than 30 kW, preferably more than 50 kW, in particular more than 70 kW. Furthermore, it is preferred that the electric machine provides a speed of more than 5,000 rpm, particularly preferably more than 10,000 rpm, and very particularly preferably more than 12,500 rpm.

[0019] According to an advantageous embodiment of the invention, a number of, and preferably all, of the electrical conductors have a substantially rectangular cross-section, the advantage of which is that the stator windings can be formed using commonly available standard electrical conductors, which is particularly advantageous in terms of the manufacturing costs of the stator.

[0020] According to a further preferred development of the invention, several, preferably all, electrical conductors have substantially the same profile in cross section, which allows the components and manufacturing complexity of the stator to be kept small and also contributes to a cost-efficient manufacturing process.

[0021] Furthermore, according to an equally advantageous embodiment of the present invention, at least one of the electrical conductors arranged in at least one of the stator slots has a contour that varies over its axial extension through the stator slot, such that the width extends radially and the height extends circumferentially in the corresponding stator slot. According to a particularly preferred embodiment of the present invention, the contour that varies over its axial extension through the stator slot can be caused by the twisting of the electrical conductor around its longitudinal axis. In principle, it may also be preferable for the electrical conductor to be continuously twisted, i.e., for the electrical conductor to have a kind of "twist" and four flow paths that rotate around the electrical conductor in its axial extension. The cross section of the electrical conductor can be either rectangular or square. The cross section of the flow paths can be directly influenced by the geometry of the electrical conductor.

[0022] Furthermore, the invention can be further developed in such a way that at least one of the electrical conductors arranged in at least one of the stator slots, in a corresponding stator slot, has a width extending radially and a height extending circumferentially, is radially surrounded in the stator slot by electrical conductors each having a width extending circumferentially and a height extending radially, whereby a particularly advantageous winding pattern can be realized and particularly effective cooling of the electrical conductors in the stator slots can be achieved, as has also been shown by tests and simulations by the Applicant.

[0023] In an equally preferred embodiment of the invention, the electrical conductor has an insulator on its outer side.

[0024] It may also be advantageous to further develop the invention so that the ratio of width to height of the electrical conductors is between 1.01:1 and 1.5:1. The Applicant has been able to demonstrate in tests and simulations that within this ratio range particularly efficient groove cooling can be achieved in a particularly simple manner.

[0025] According to a further preferred embodiment of the invention, the electrical conductors are arranged substantially identically in a number of, preferably all, stator slots, which reduces the complexity of manufacturing the stator as much as possible.

[0026] Finally, the present invention can also be advantageously configured in such a way that an even number of electrical conductors of a first group are arranged in a plurality of stator slots such that in the corresponding stator slots the width in each case extends radially and the height in each case extends circumferentially, and an even number of electrical conductors of a second group are arranged in this plurality of stator slots such that in the stator slots the width in each case extends circumferentially and the height in each case extends radially.

[0027] In a highly preferred embodiment of the present invention, the stator windings are configured as hairpin windings. In the case of electrical conductors configured as hairpins, such as those that can be used in hairpin windings, the rotation of the electrical conductors relative to one another can also have a beneficial effect on the winding heads, since in this case, in principle, some deformation of the electrical conductors would occur anyway, which could potentially be simplified by additional shaping.

[0028] Finally, in this context, it may also be preferred that at least one hairpin of the hairpin winding has a first electrical conductor and a second electrical conductor parallel to the first electrical conductor and having a substantially identical cross-sectional profile, the first electrical conductor being rotated relative to the second electrical conductor by at least one turn of approximately 90° about the longitudinal axis of the first electrical conductor.

[0029] Without limiting the general concept of the invention, the invention will now be explained in more detail with reference to the drawings. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. [Figure 2]FIG. 1 is a perspective view of a hairpin. [Figure 3] 1A-1C are schematic perspective views of a hairpin with two electrical conductors that rotate relative to each other and a hairpin with a twisted electrical conductor. DETAILED DESCRIPTION OF THE INVENTION

[0031] 1 shows a stator 1 for an electric radial flux machine comprising a stator body 3 having a plurality of stator teeth 4 distributed around the circumference and a stator slot 5 formed between the stator teeth 4 and extending axially through the stator body 3. Arranged in the stator slot 5 are stator windings 6 having a plurality of electrical conductors 7 capable of carrying electric current. The electrical conductors 7 have an insulator 12, e.g., insulating lacquer, on their outer sides. The stator slot 5 is generally U-shaped with straight, radially extending slot walls through which a cooling fluid 12 can flow.

[0032] Since the stator 1 is configured for an internal rotor, the stator slots 5 along their radial extension have slot bases 8 at their radially outer ends and slot openings 9 at their radially inner ends. In principle, it is also conceivable that the stator 1 is for an external rotor, in which case the stator slots 5 along their radial extension would have slot bases 8 at their radially inner ends and slot openings 9 at their radially outer ends, but this is not shown in the drawings.

[0033] The electrical conductors 7 of the stator windings 6 have a width 19 and a height 10 in cross section, with the width 19 being greater than the height 10, as can be clearly seen in Figure 1. A portion of the electrical conductors 7, for example, the electrical conductors 7 that rest on the slot bases 8, are positioned within the stator slots 5 such that the width 19 extends circumferentially and the height 10 extends radially within the stator slots 5.

[0034] Additionally, electrical conductors 7 are also positioned within the stator slots 5 such that the width 19 extends radially and the height 10 extends circumferentially at the corresponding stator slots 5. Together with the stator slots 5 and radially adjacent electrical conductors 7, they define cooling channels for cooling fluid 12 that passes axially through the stator 1. The cooling fluid 12 dissipates heat from the stator windings 6 or stator slots 5.

[0035] All electrical conductors 7 have a substantially identical rectangular profile in cross section. In the embodiment shown in accordance with the invention, the ratio of width 19 to height 10 of the rectangular electrical conductors 7 is between 1.01:1 and 1.5:1. In the embodiment of FIG. 1 , one of the electrical conductors 7 arranged in one of the stator slots 5 is radially surrounded by electrical conductors 7 whose respective widths 19 extend circumferentially and whose respective heights 10 extend radially within the stator slot 5. This results in three radially consecutive electrical conductors 7 in each case forming a double T-shaped profile in cross section. It is clear from FIG. 1 that the electrical conductors 7 are arranged in a substantially identical manner in all stator slots 5, i.e., two double T-shaped groups of electrical conductors 7 are positioned radially above each other within the stator slot 5.

[0036] In this case, an even number of the electrical conductors 7 of the first group 14 are arranged in the stator slots 5 such that the width 19 of the corresponding stator slot 5 in each case extends radially and the height 10 in each case extends circumferentially, and an even number of the electrical conductors 7 of the second group 15 are arranged in the stator slots 5 such that the width 19 of the corresponding stator slot 5 in each case extends circumferentially and the height 10 in each case extends radially. This even number is particularly advantageous when using hairpin windings.

[0037] The stator winding 6 known from Figure 1 is configured as a hairpin winding 16. A hairpin 13 of this hairpin winding 16 is shown in Figure 2. The hairpin 13 includes a first electrical conductor 7a and a second electrical conductor 7b that is parallel to the first electrical conductor 7a and has substantially the same cross-sectional profile.

[0038] As shown in the top diagram of FIG. 3, the first electrical conductor 7a in the first embodiment of the hairpin 13 can be rotated by approximately 90° relative to the second electrical conductor 7b about the longitudinal axis 11 of the first electrical conductor 7a.

[0039] Alternatively or additionally, it is contemplated that the first electrical conductor 7a could have a thread-like profile that varies over its axial extension through the stator slot 5, as shown in the lower diagram of Figure 3. This varying profile over the axial extension of the first electrical conductor 7a results from the electrical conductor 7a twisting about its longitudinal axis 11.

[0040] The present invention is not limited to the embodiments shown in the drawings. Therefore, the above description is not to be considered limiting, but rather illustrative. The following claims should be understood to mean that the described features are present in at least one embodiment of the present invention. This does not exclude the presence of additional features. Where "first" and "second" features are defined in the claims and the above description, this designation serves to distinguish two features of the same type without defining a priority. [Explanation of symbols]

[0041] 1 stator 3 Stator body 4 Stator teeth 5. Stata Slot 6 stator winding 7 Conductors 8 slot base 9 Slot opening 10 Height 11 Longitudinal axis 12 Cooling fluid 14 First Group 15 Second Group 16 Hairpin Winding 19 width

Claims

1. A stator body (3) having a plurality of stator teeth (4) distributed around the periphery and stator slots (5) formed between the stator teeth (4) and extending axially through the stator body (3); and a stator winding (6) having a plurality of electrical conductors (7) arranged in the stator slots (5), wherein the stator slots (5) along their radial extension have a slot base (8) at their radially outer end and a slot opening (9) at their radially inner end, or the stator slots (5) along their radial extension have a slot base (8) at their radially outer end and a slot opening (9) at their radially inner end. a stator (1) for an electric machine, comprising: a stator winding (6) having a slot base (8) and a slot opening (9) at a radially outer end, the electrical conductors (7) of the stator winding (6) having a width (19) and a height (10) in cross section, the width (19) being greater than the height (10), the electrical conductors (7) being disposed in the stator slots (5) such that the width (19) extends circumferentially and the height (10) extends radially in the stator slots (5); and a cooling fluid (12) capable of flowing through at least one of the stator slots (5), At least one of the electrical conductors (7) is at least partially disposed in at least one of the stator slots (5) through which the cooling fluid (12) can flow, such that the width (19) extends radially and the height (10) extends circumferentially in the corresponding stator slot (5); A stator (1) for an electric machine, characterized in that, among three electrical conductors (7) arranged radially consecutively within the stator slot (5), one electrical conductor (7) arranged so that the width (19) extends radially and the height (10) extends circumferentially is surrounded on both radial sides by an electrical conductor (7) whose width (19) extends circumferentially and whose height (10) extends radially.

2. 2. A stator (1) according to claim 1, characterized in that the electrical conductors (7) have a substantially rectangular profile in cross section.

3. 3. A stator (1) according to claim 1 or 2, characterized in that the electrical conductors (7) have substantially the same profile in cross section.

4. 2. A stator (1) according to claim 1, characterized in that at least one of the electrical conductors (7) arranged in at least one of the stator slots (5) has a contour that varies over its axial extension through the stator slot (5), such that in the corresponding stator slot (5), the width (19) extends radially and the height (10) extends circumferentially.

5. 5. A stator (1) according to claim 4, characterized in that the contour that varies over the axial extension through the stator slot (5) is caused by the electrical conductor (7) twisting about its longitudinal axis (11).

6. 2. A stator (1) according to claim 1, characterized in that the electrical conductors (7) have an insulator (12) on their outer sides.

7. A stator (1) according to claim 1, characterized in that the ratio of the width (19) to the height (10) of the electrical conductor (7) is between 1.01:1 and 1.5:

1.

8. 2. A stator (1) according to claim 1, characterized in that in a plurality of said stator slots (5), said electrical conductors (7) are arranged in a substantially identical manner.

9. 2. A stator (1) according to claim 1, characterized in that an even number of first groups (14) of electrical conductors (7) are arranged in a plurality of stator slots (5) such that, in a corresponding stator slot (5), the width (19) in each case extends radially and the height (10) in each case extends circumferentially, and an even number of second groups (15) of electrical conductors (7) are arranged in a plurality of stator slots (5) such that, in a corresponding stator slot (5), the width (19) in each case extends circumferentially and the height (10) in each case extends radially.

10. 2. A stator (1) according to claim 1, characterized in that the stator winding (6) is configured as a hairpin winding (16).

11. 11. A stator (1) according to claim 10, characterized in that at least one hairpin (13) of the hairpin winding (16) comprises a first electrical conductor (7a) and a second electrical conductor (7b) having substantially the same cross-sectional profile and parallel to the first electrical conductor (7a), the first electrical conductor (7a) being rotated at least once by approximately 90° relative to the second electrical conductor (7b) about the longitudinal axis (11) of the first electrical conductor (7a).

Images